﻿#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    void duplicateZeros(vector<int>& arr) {
        int cur = 0, dest = -1, n = arr.size();
        while (cur < n) {
            if (arr[cur])
                dest++;
            else
                dest += 2;
            if (dest >= n - 1)
                break;
            cur++;
        }
        // 2. 处理⼀下边界情况
        if (dest == n) {
            arr[n - 1] = 0;
            cur--;
            dest -= 2;
        }
        // 3. 从后向前完成复写操作
        while (cur >= 0) {
            if (arr[cur])
                arr[dest--] = arr[cur--];
            else {
                arr[dest--] = 0;
                arr[dest--] = 0;
                cur--;
            }

        }
    }
};